Vibrating screen



May I4, 1929.

G. A. OVERSTROM IVIBRATING'SCREEN Filed Feb. 23, 1924 7 Sheets-SheetINVENTOR ATTORNEYS May 14, 1929. G. A. OVERSTROM VIBRATING S GREEN FiledFeb. 25, 1924 7 Sheets-Shea? ATTORNEYS May 14, 1929.

. G. A. OVERSTROM VIBRA'I'ING SCREEN Filed Feb. 25, 1924 7 Sheets-SheetINVENTOR WM Q BY QTT YZIZ BYS May 14, 1929.

G. A. OVERSTROM 1,713,143

VIBRATING SCREEN Fild Feb. 23, 1924 7 Sheets-Sheet 4 9 1 ATTORNEY-5 y14,.1929- a. A. OVERSTROM 1,713,143

VIBRATING SCREEN Filed Feb. 23, 1924 7"Sheets-Sheet. 5

9) ATTORNEY y 14, 1929- G. A. OVERSTROM 1,713,143

'VIBRATING SCREEN Filed Feb. 23,1924 .7 Sheets-Sheet 7 )6 ATTORNEY 3 6'11 ENTOR Patented May 14, 1929.

"tJ NITE D STATES GUSTAVE'A. ovsnsrnom, or rAsAnnn'A, cAmFonNIA.

'VIBBATING SCREEN.

Application filed February 23, 1924. Serial No. 694, 538.

This invention relates to vibrating screens, and particularly to screensto which are imparted a very high frequency -of vibration to effect theseparation and grading of various materials, such as sand, gravel, ores,coal, or

the like. i 1 R a The object of'the invention is to provide a vibratingscreen which is simple in structure, economical to manufacture andefiicient in operation, and wherein a high rate of vibration of thescreen or screens is secured by means of an unbalanced pulley device;

A further object of the invention is to provide a screen structure ofthe nature referred to, wherein the rate of vibration may be altered orvaried by means of removable and replaceable weights;employed to securethe unbalanced action of the vibrator.

A further object is to provide a simple and compact'structure ofunbalanced pulley to impart the vibratory movements to the screen, andwherein-efficient lubrication of the tpulley structure is securedwithgut danger 0 leakage through centrifugal orce whenthe unbalarcedpulley is driven at a high rate of s cc A further object is to providemeans to compensate for unequal wear due tothe unbalanced condition ofthe pulley.

vide an outside support'ng framework within which the screen box issuspended and vibrates, further improved structure .of' delivery chutes.

. A further object is to provide an improved screen cloth structure andmounting and ten-- Referring to the accompanying draw ings:-

. "Fig. lisaj top plan view of. a vibrating I screen. embodying theprinciples of my inveni 7 tion.

A further object of the invention is to.pro-- bject is to provide asimple and Other objects of the invention will appear ts substantiallyin the fully hereinafter set forth, as shown in the ing a preferredembodiment of'my invention,

Fig. 2 is a view in side elevation of the same. v

Fig. 3 is a view .in elevation of the head end of the machine.

Fig. 4 is a similar view of the tail or delivery end.

Fig. 5 is a view iiivertical'central longir tudinal section through themachine on the line 0,0, Fig. 1, the delivery chutes being omitted.

Fig. 6 is a broken view in side elevation showing on a larger scale onepf the spiral springs employed structure.

Fig. 7 is a view in transverse section through one side of the vibratingportion of the structure illustr'ating'one form of means for supportingthe side edges of and transversely tensioning the screen cloths. Fig. 8is a similar view through the delivery end of the same, illustrating aform of means to suspend thevibrating 65 for supporting and securing thedelivery ends of the screen cloths. I

'Fig- 9 is a similar view through the head or receiving end. I

Fig. 10 is an enlarged broken dethil view in section illustrating themanner of securing the desired transverse and head end tensioning of thescreen cloths.

3 Fig. 11 is a. view in transverse section through the vibrating portionof the structure. I

Figs. 12 and 13 are broken detail views in transverse sectionillustrating a modified-an, rangement for securing ,and tensioning the,screen cloth. s I

- Fig. 14 is a detached detail view, partly in section, showing thestructure of nested and 0 Fig. 16 is a view in transverse section of thesame on the line A, A, Fig. 1 5. T

Fig. 17 is a similar view on the line-B, B,

.Fig. 15. J ".j y

Fig.18 is aviewfliin end elevation. of the structure shown in Fig.15;

Fig. 19 is a view 1n transverse section showtrate the structure shown inFig. 19.

' reference Fig; 21 'is a detail view illustrating a preferredarrangement of tensioning binder for the edge of the screen cloth.

The same part is designated by the same numeral whereverit occursthroughout the several views;

In my pending application for patent, Serial No. 413,376, filedSeptember'28 1920, Patent Number 1,621,949, March 22, 1927, I haveshown, described and claimed a vibrating screen structure whereinthe'screen' box or screen cloth carrying frame is yieldingly suspendedon springs and is vibrated by means of a rotary unbalanced pulley.

.My invention relates generally to vibrating screens of the same typeand mode of oper- M31011, and consists in certain features ofconstruction incorporated therein, and in certain'improvements thereon,all as will be more fully pointed out hereinafter.

In my prior application, above referred to, I have shown the spiralsprings by which the vibrating screen box is carried and suspended, asbeing held by clamps bolted to a stationary beam; According to thepresent invention, I propose to incorporate the spring supporting beaminto anenclosing framework for the screen box,'the springs beingreceived and resting in boxes bolted to the enclosing framework, or abeam member forming part'thereof, and being held'in place by means ofclamp members bolted to said boxes and extendingpartially over the'upper portions of the springs.

Referring to the drawings, the screen box enclosing framework is shownin 'this' instance as including side members each having an upperand alower longitudinally extendingbeani 1, 2, respectively disposed inparalIel relation to each other, and suitably connected and braced toeach other by means of vertical posts 3 and brace members 4 and also,ifdesired or required, by bolts 5, The

corresponding ends of the upper beams 1 at opposite sides of the machineare connected together, as, for instance, by means of bolts 6, while thelower beams 2 at opposite sides of the machine may be connected to etherin any suitable manner, as by means 0 cross beams 7 and bolts 8,

An enclosing framework, such as above described, for the vibratingscreen box affords the very important advantages of a protectionfo'r thescreen box in transportation and in handling and setting up the machinefor operation, the lower beams 2 constituting supporting base membersfor the entirestructure. In addition, I am also en- V flflllledjo moreaccurately and satisfactorily allel relation to each other at oppositesides of the structure, said stringers at each side being connectedtogether by vertically disposed side plates 11 and bolts 12, and thecorresponding stringers at opposite sides of the box are connectedtogether by the cross members 13, 14. The. cross membersl-S, spacedapart from each other, and preferabl located at a point intermediate theends \of he box frame serve to connect the upper stringers 9, and theyalso form part of the In the ill-usstructure in which the unbalancedpulley is I mounted, as will be hereinafter. 7

It will be observed \that the screen box frame is of generally cubical:shape, and

should be of such relativ eisize as to be re more fully e xplainedceived and tofreely move or vibrate between the side portions of theenclosing framework when properly positioned in place and suspendedtherein. g

In the construction and operation of vibrating screen structures, I havefound it exceedingly desirable to provide means by which the screencloths may be easily and expeditiously removed independently of eachother in order that various kinds of material may be handled on the samemachine by replacing the screen cloths so as to use screens of therequired mesh, according to the particular character of material to bescreened, and also in order that any particular screen cloth may berepaired or replaced by a new one, in case of injury or wear, withoutdisturbing the other screens. I therefore propose, inaccordance with mypresent invention, to employ independent screen units each consisting ofaframe structure and a screen cloth assembly, and I removably mount eachscreen unit in the screen box structure above described. To accomplishthis result, I form guide ways or channels on the innerface of each sideplate 11 of the screen box, into which slide the side members of thescreen units. V

The frame structure of each screen ,unit consists of side members orstringers 16, and intermediate parallelmembers 17. These stringers andintermediate members are pref- 'erably of wood, and are rigidlyconnected together into a unitary frame structure by,

imparted to the screen box, prefer that the cross'connections 13 betubular, particularly where screens of considerable width are to be -Iconstructed. My invention, however, is not to be limited or restrictedin this respect. The

inner faces of the side stringers 16, and securing bolts 19 serve torigidly secure the side stringers lti together. Where tubular crossmembers 18 are used, these securing and wearing plates may serve asclamping bolts may pass longitudinally through thetubes 18I I 1 a Thescreen cloth assembly in one embodiment of my invention consists of asub-screen cloth 20 of comparatively large mesh and a limiting screencloth 21 of relatively smaller mesh, placed fiatwise upon eachother,,-the limiting screen cloth being uppermost. The side edges andthe ends of the superposed screen cloths are folded over uponthemselves, as more clearly shown in Fig. 10. A metal binder strip 22 isformed with a portion thereof bent or folded over upon itself, suchfolded portion being received within the'fold' of the edges of thescreen cloths. One leg of the folded portion of the binder strip is thenbent upwardly and outwardly over the edge portions of the screen clothsso as to embrace the same. The edge of the other leg portion of thefolded metal strip is preferably turned upwardly to a slight extent, asindicated at 23. The screen frame structure and the screen clothassembly are cohstructed and assembled separately. The frame structureis first slid into place in the channels 24 of the side plates 11 of thescreen box, and-then the screen cloth assembly is slid into the box, theedgesof the screen cloths being received upon the upper faces of theside stringers 16. If desired, andin order to facilitate the insertionand removal of the screen cloth assembly into place upon the screenframe striicture metal for the upper surfaces of the stringers. Thescreen cloths rest intermediate their edges upon the intermediatemembers 17 of the screen frame structure. These intermediate members17are preferably faced on their upper surfaces with metal strips 26which areoval or crown shaped at their upper supporting surfaces. Theintermediate portions of the screen cloth rest .on said strips 26 whichextend from end to end of the screen frame.

At the front or feed-in end of the screen box the ends of the screencloths are folded ver I upon themselves and are engaged. by metal binderstrips of the same formation and in the same'way; asabove described withrefer ence to the edge portions of the cloths. These ..end portions ofthe screen cloths with their associatedmetal binder strips are receivedon wearing plates 25 carried by cross members of the screen framestructure,

The loweror deliveryends of the screen cing plates cloths are bent orfolded over an edge flange of transverse channel members 28 of thescreen frame structure, see Fig. 8, and are clamped therein by an angleplate 29, bolted to the channel members 28. I

If desired, and as shown in Figs. 7, 8 and 9,.where several sets ofscreen units .are employed in the same machine, the lowermost" screenassembly may be received and rest at its ends and edges on the stringers10 andl of the screen box, said stringers having earing plates 30,similar in purpose and unction to the wearing" plates 25, above referredto. In such ca.se,'the intermediate members 17 are 'fastened to thetransverseconnections 14 of the screen box.

J The transverse and longitudinal tensioning of the screen cloths may beeffected 1n var1- ous -ways. In. the arrangement shown in Figs. 7, -10and 11, the transverse tcnsioning.

of the screen cloths is accomplished by means of stretcher plates,disposed to extend longitudinally of the screen cloth assembly at theedges thereof. These stretcher plates are disposed vertically and restat their lower edges upon the upper surfaces of the edge portions 23 ofthe screen edge engaging strips 22, and bear laterally and outwardlyagainst the bends of the strips 22 which receive the folded over edgesof'the cloths. At their upper bearing against the stringers 16, therebymost simply and efficiently stretching and tensioning the screen clothstransversely. In order to permit the fulcrunnng movement referred to ofthe stretcher plates, the openings 33 in the side plates 11 throughwhich the stretcher bolts,32pass are of larger area than thesize of thebolts. thereby permitting the tilting of the bolts during the stretchingmovements of the plates 31. Also to still'further facilitate th1sfulcruming action of the stretcher plates, instead of the upper edges ofsaid plates bearing flatwise against the inner surface of thestringers-16, I prefer to chamfer olfor bevel the lower inner edges ofvsaid stringers, as indicated at 34E, the fulcrum edge of the stretcherplate being received against the inclined surface afforded bythischamfer. A similar arrangement for tensioning the screen cloth unitsendwise is shown in Fig. 9,

as applied to the upper or feed-in end of the said cloths. In this casethe stretcher plates extend transversely across the screen-cloth unitand fulcrum at their upper edges against chamfered or beveled surfaces36 of the cross members 27, said plates being tightened intostretching'relation by bolts 37. If desired,

' and as shown, and in order to facilitate the has been effected saidwedges are driven up assembly in place or removal'of the stretchertight, thereb securely clamping and holding plates the cross members 27are cut away on all the parts 1n their relative positions foreflitheir'outer lower portions, as indicated at 38, cie'nt operation. In7 order to protect the to afford space for the insertion or removaledges of the screen cloths which engage over therethrough of the saidplates. It will be the flanges of the stretching beams, I may understoodthat the transverse tensioning of interpose a metal strip between thebearing the screen cloths is effected by the stretcher surfaces of thecloth and beam flanges. plates at opposite side edges of the ClothsWhere a heavy screen cloth is used, a metal WOfking against each other,While the lOIlg'istrip 46 bent to channel shape is slipped over tudinaltensioning is effected by the end the flan e of the beam and the edge ofthe stretcher plates at one end of the cloths screen c 0th isthendoubled over this strip. working against the clamping means which Wh liht l th arecefnployed, t h

secure and hold the opposite ends of th lid strips 47,48 are preferable.These stripscloths. It will also be observed that by 6111- are nestedinto each other and are disposed ploying edge stretcher plates-whichextend one on the outside and one on the inside of lengthwise throughoutthe whole length 0f the fold in the edge of the cloth, as shown in Y Ythe cloths and end stretcher plates which eX- Fig. 12. This arrangementnot only effectutend the entire transverse wldth of the cloths," allyprevents slipping ofthe screen cloth when an eflicie'nt and uniformtenslonlng f the stretched, or while being stretched, but it also screenclo is effected throughout the entire allows the flimsy screen cloth tobe easily I area of the screens.

. p slipped into place on .the stretching beams In Figs. 12 and 13, Ihave shownmodified In case of the use of screen cloths of screen cloths,whereln the edges of the screen v ry fine i a d h, I may o l use thcloths 39are folded over the flanges of chansingle bent stamping 46 andsolder the cloth.

nel beams 40, 41 disposed at oppositesides t it,

of the screen box. One member 40 of each \Vh d bk r t i tr t hi beams 40pair of these channel beams is adjus ably are employed, it is difiic'ultto slip the screen secured by bolts 42 to the inner walls of the clothsinto place thereon after sald beams are side plates 11 of the screenbox, while the secured inplace in the box. In suchcase, the other member41 of such pair is permitted a screen cloths are applied to the beamsand fulcruiming' action when tightened upby 1ts then the latter aredropped into place within securing bolts 43, to stretch and tension thethe screen box. To permit this, I rivet 0r. screen cloth. In this case,the channel beams weld, or otherwise secure, nuts 49 to theout- 40,coacting with cleats or spacers 44, or otherwardly presenting sidesurface of the beam wise, serve principally as clamping and holdand atappet bolt 50 is inserted through the without removal of thelat'terfrom the screen structures for stretching anditensioning the b x,

3 ing devices for the edges of the screws while. side plate ll of thescreen box to thread into If desired, however, both or either of thestretching adjustment of the beam.

the beams 41 effect the desired tensioning. the nut- 49, in order toeffect the desired beams 40, 41, may be employed to effect the In Figs.19, 20 and 21, I have shown an tensioning action and in Fig-13 I haveshown arrangement for supporting and tensioning variations in thisrespect; For example, the the screen cloths which I have found mostupper left-hand an lower right hand areflicient in use and which,because of its adrangement shown in this figure may be em-. vantageousfeatures, I prefer in many cases ployedto apply independent tensioningto-' to employ. one edge only of a single screen cloth while In thisstructure, the arrangements shown at the 'upper. rightscreen cloths anduse a single cloth 6.1 for each hand and lower left hand portionssimulscreen unit or element. Where alight screen taneous stretching iseffected of twoadjacent cloth is used, the edge of the cloth is firstscreen cloths. Where the twin tensioning folded over upon itselfas'indicated at 62, means are employedthe channel members 40 Fig. 20,and then the folded portion is again themselves form, spacers, but whereindifolded over uponthe body of the cloth to vidual tensioning is to beeffected the s' acers 'IOI'II1 a wider fold, the outer edge of the bend44 are used. The members 44, if desire may of which is indicated at 63.The binder strip serve not only to coact with thebeams 40 or is bent orfolded upon itself thereby forming 41, but also tqprotect the sideplates 11 of the an edgebend 65, which is slipped into and screen boxagainst wear, as'well as to hold bottoms against the inner surface ofthe edge the beams pressed solidly to the lower beams bend 63 in thescreen cloth. The inner por- 10 of the screen box. Wedges, indicated-attion of the upper leg of the binder strip'is- 45, are employed incarrying out the funcbent-upwardly and outwardly to form the-f tion ofholding down the beams rigidly to the bend 64' into which the edge fold62 ofthe base beamslO. These wedges are not driven screen cloth enters,but, in practice, I prefer up tight until the screen cloths have beenthat the screen cloth bond 62 does not bottom "properly tensloned, butwhen such tensioning" against the lnner surface of the bend 64 m Idispense with one of the the binder strip, thereby leavin a clearancespace 66 between the edge of t e cloth and the inner surface of the stribend 64. The up'per'leg portion of the bin er strip extends outward yfrom the bend 64 and its extreme edge portion 67 is downwardly bent tohug over the outer surface of the bend 63 in the cloth. The inner edge68 of the binder strip. is turned upwardly and the corresponding edgeof'the wear plate is'turned downwardly, as indicated at 30. This permitsthe vertical vibrations of the cloth to be efiected without undue wearin working or bend ngover sharp edges, thereby greatly increasing thelife of the cloth.

Where a comparatively heavy cloth is employed I find that theinitial-edge bend 62 of the cloth can be dispensed with, as indi- Icated in Fig. 21, but the other features above described with referenceto theformation and application of the binder strip tothe edge of thescreen cloth are retained. n

l have found in practice that in handling certain kinds of material, acutting and rupso as to take the impact of the'screen cloth when invibration, upon the armorsurface 26. In practice, a single wear strip'70 may be applied to the under surface of :the cloth or, andpreferably, a pairof such stri s are' clainpedttogether with the screenclot disposed between them,'as shown in Fig, 20. In operation, thescreen cloth, clamped, ten-.

- sioned and supportedas above described, not

'onl vibrates or, move'sfwith the box in which its mounted but angindependent vertical vibratory movement is setup in the stretched clothwhich causes the wear or hammer strips I 70 to repeatedly strike sharplythe upper oval surfaces of the armor strips 26. I have found that thisaction serves to keep the screen cloth .clean,even-when operating on.damp clay material. The wear strips 70 prevent particles of the materialbeing handledfrom lodging on the armor 26, and hence wear on the screencloth at this point is eliminatedv a I have also found in the practicaloperation of screen structures embodyingm invention,

that I can dispense with then stretching of thescreen cloth and also, insome instances,

I can'dispense with the stretching devices at I a one side edge of thecloth,,as I'liave found that 7 when the screen cloth is once clamped andstretched edgewise or transversely to the desired tension,furtheriadjustment of the tensioning is not ordinarily required,particu-- larly as long as the same kind of material is, being handled(I sometimes a thin layer ,of belting, cloth, rubber, or even wood,between the wear plate 25 and the stringer 16, or 14, as indicated at72.- I The spring suspension for the screen .box

find it-desirable to interpose 70 witliin'the outer base frame unit, asshown in the drawings, is in accordance with the disclosures of my priorapplication, above referred to. Mounted in boxgs 51, Qntlie upperlongitudinally extending stringers -9 of the screen box, and held inplace therein by clamp [brackets 52, are the members 53, shown in thisinstance as tubular pipe sections, one near each end of and arranged toextend transversely across the screen box. The ends of 7 these members53 extend beyond the side stringers 9, and mounted on and secured tothese projecting ends are the spiral springs 54. These spiral springsare seated in boxes 55 mounted on and boltedto the upper-longitudinalside beams 1 of the base frame structure, and are securely clamped andheld therein by clamp plates 56. In this manner q the screen box isyieldingly suspended within the base frame structure. It is immaterial,so far-as my present invention is concerned, whether the .pipe sections53 are stationarily clamped and held in boxes on the screen box or inboxes on the base frame, in which latter-'1 case they suspension springswill be mounted in boxes on the screen box stringers. In the I one casethe pipe sections 53 will vibrate with the screen box and in the othercase they do not. In either case, the entire suspension of the screenbox is taken up b the vspiral springs and the weight imposed by thesuspension is applied in vertical lines diametrically of the spiralsprings. Thus the screenbox and screen units carried thereby, as well asthe load of material under treatment, are

free to yieldinglyvibrate under the action i of-the rotating unbalancedpulley structure 'now to be described. v

Suitably mounted at i'tsends in seats provided therefor instringersections- 57, con

necting the cross members 15. ofthe screen box, is a hollow shaft 58'upon vhich is mounted the unbalanced pulley through the rotations ofwhich the suspended screen-box is vibrated. The ends-of this pulleyshaftare closed by means of. plugs 59, see Fig. 15. Shaft 58 is rigidlyclamped in its seats in the stringer sections'57 by means of clampplates 60, suitably bolted or otherwise secured to I the stringersections 57. a I At-or near each end thereof, the shaft 58- is providedwith threaded or' tappedholes which extend transversely of the shaft tothe hollow lfo're thereof. In one of these'tappe'd holes an oil stopcock 73' is screwed and in the other; of said tapped holes alsolid plug"'74 is'screwedv In practice, I prefer to make said stop cock and pluginterchangeable.

V -The clamp plates 60 at each endof the shaft I danger of shearing offthe oil sto cock which it is necessary to provide in orer to afford"means for supplying lubricant to the unbalanced pulley structure, whichstructure I will now describe, particular reference being had toFigs.15, 16, 17 and 18. A

Mounted upon the enlarged central portion 75 of the shaft 58 is thepulley body 76, a bushing or lining sleeve 7 7 bein preferablyinterposed between the pulley bor y and shaft. The driving belt (notshown) through which around .the pulley body 76. At each. end thereofthepulley body 76 has formed therewith or carries a radial web or flange78, which in turn has formed therewith or carries an annular band 79,the radial web or flange 78 being centrallydisposed with r'ef-' erenceto said band. With this arrangement,

- one edge of each band 79 extends inwardly over and in encompassingrelation with respect to the adjacent end of the-pulley body to form ahousing within which the unbalancing weights are mougted, as will bepresently inore fully explalned. The other edge of each band 79 extendsoutwardly and is contracted radiall towards the shaft 58, into a ring80, whic is interiorly threaded to receive a threaded collar or plug 81mounted with a packed hearing, as indicated at 82, upon the shaft. Aplate or disk 83 is mounted against the outer faces of the ring 80 andcollar or plug 81. This arrangement forms a closed chamber 84 to receiveand contain the oil or other lubricant, and-ensures against leakageofthe oil under thf centrifugal force to which it is subjected 'hen thepulley is in. working operation. To still further insure against oilleakage, a packing material, 85, is interposed between the plate or disk83 and the-faces of the hub ring 80. By contracting the outer edge ofthe band 79 to form the ring portion 80 of smaller diameter, thethreaded engagement of the collar or plug .81 into said ring is broughtinside the area,of greatest centrifugal force applied to the oil inchamber 84 when the pulley is preventing oil leakage.

in operation, thereby'still further aiding in Should, however,notwithstanding these safeguards against 011 leakage, there be anyleakage of the oil, .I provide an oil catch or drip chamber 86,consisting,'inthe illustrative fornr shown, of a hub portion 87, mountedupon and secured to the shaft 58, and having a portion 88 whichoverhangs the ring 80.

' In order that the oil ameter'than the other holes 91. .101 formssomething of a secondary reservoir contained in; the reser- 1 voir orchamber 84 may be efficiently supplied to the various bearings ahdsurfaces requirmg lubr1cat1on, I provide oil scoops 89 in the form ofpipe sections bent or curved in a direction opposite to that of therotation of thepulley body.- These oil scoops are located within the oilchambers 84 and are screwed into threaded openings formed transverselyin the shaft 58, or the enlarged portion of said shaft, and extending tothe bore of said shaft, as indicated at 90. In operation th' e scbopspick up or receive. the oil and con uct it to the bore of the shaft andthence throu h suitably disposed holes 91 and grooves 92 to tributingrooves 92 preferably extend longitudina 1y of the pulley shaft andparallel to the axis thereo they ma be threaded into holes in a collar93 whic is fastened to the shaft with the holes in the shaft and collarinline or register with each other. This structure very greatlysimplifies and facilitates the manufacture and assembly of the parts,thereby cheapening the manufacturing costs. By employing bent pipesections, I avoid the necessity of eoring out castings and eliminateroughness in the surface. of the bore of the .the' surfaces to'belubricated. The oil dis- Instead of threading v the scoop mefnbersdirectly ,into the shaft, 1 the unbalanced pulley is rotated engagesscoops, thereby preventing the danger -of I clogging through thecollection of sand, dirt, .or other foreign matter in such bores, whileat the same time I secure and maintain uniformity in size of the scoopbores, and hence a more uniform oil distribution is effected. In orderto increase the efiiciency of the oil distribution, I provide anenlarged annular re i cess 101', in the inner surface of the bushing 77,at about the mid-length of said bushing, and I make the hole 91 from thebore of theshaft into this annular space, of larger di This space forthe oil, the longitudinally extending grooves 92 terminating in thisspace or reser- V011.

I If desired, drain cocks 102 maybe provided for the chambers 84, 86,see Fig. 18.

The unbalancing of the pulley structure may be secured in various: Ways.I .have shown a very simple, effective and desirable arrangement,towhich, in its broadest scope, my invention is not to be limited orrestricted, wherein I mount rem vable weights within the housingafforded by the inwardly extendingoverhang of -the-inner 'edge of theband ,79. Within this housing are disposed studs 94.which extendradially inwardly and are spaced a art, from each other at equaldistances. n the particular arrangement] shown, and which, in practice,Ihave found effective and eflicient, I employ four offthese studsand-locate' them ninety degreesapart. The overbalancing weights consistof akseries of segmental sections or members which are nestedwithin eachother. These sections-are curved at their outer and inner edges to thecontour, respectively, of the inner surface of the overhanging portionof band 79, and of the exterior surface of the pulley body, so as to fitsnugly therebetween, and they are of a length to fit snugly'between twoadjacentstuds or'pins 94. These weight members are of U-shape inlongitudinal section, as shown in Fig. 14.1 The outermost member 95 ofthe nested series, which I will call the masterweight, has the spacedapart pins-ors'tuds 96 extending laterally from its inner face, whichform supports for'the other weight sections which are formed with holesthrough which with relation to each other and to the master p Thisaffords a ver a tween another pair, the wear of the bushjn 77 in itsbearing on the shaft is distribu Pl weight. This enables me to secure adesirable range of adjustment'or variation of the -un-' balancingaction. The weight. members may be 'mounted and held in place in thehousing in any suitable or convenient manner.- A sin'iple-arrangement isshown wherein the master weight is equipped at'its geometric center witha stud 98, which extends lateralf ly and outwardly therefrom and uponwhich is ivotally carrieda latch. plate 99. The end; of this latch plateare received in annular grooves formed in the inner surface of band 79and the exterior surface of the pulley body, respectively, when theweights are inserted in position within the housing. simple andconvenient means to det'acha l lock the assembled weights in place. W enit is desired to alter or vary the unbalancing action of theweights, orthe rate or amplitude of vibrations, the. latch plate 99 is released,the assembled wei hts removed and any desired one or more of t e weightmembers taken out or' replaced by'another or others and the assembly .aain placed and secured in its housing. is structure and arrangement isnot only simple-but it affords ease and speed of assembly, removal andreplacement. By removingthe weight'assembly from between any given pairof spaced studs 94, and replacing them be:

and the unequal wear due to the unbalanc condition ofthe pulley is comnsated, there ,byincreasing the life of the-Eiishing. In practice Iprefer to set the machine on an incline, the extent or grade of whichwill be varied accordin to the character of the material to be han ed,and accordingto thev direction of rotationof the unbalanced pulley. Ihave found an inclination varyin from seven to nine inches per .foot oflength delivery chute arrangement, wherein the.

These chutes, while delilvering from difl'erent is satisfactorywhen theunbalanced pulleyis e5 driven in one direction, while an inclination offrom four to seven inches per foot of length is satisfactory when thepulley is driven-in the otherdi'rection. By mounting the vibratingscreen box within its auxiliary 70 or outer supporting framework, asabove described, thereby making the structure one unitary self-containedwhole, I am enabled-to easily and quickly set up the apparatus with anydesired inclination and with more a(:- 75

curacy than has been possible heretofore.

I The material to be screened is introduced to the screen box at theupper or receiving end of the machine. I have shown a. receiving feedchute 103 for'this purpose, which receives the material and distributesit transversely across'the upper receiving endlof the upper nostvscreen.This feed chute is mountedon or carried b the screen box, and hencevibrates therewith .v This aids in properly distributing and spreadingout the material.

on to the surface of the uppermost screen;

Each screen delivers at its lower end'to its own delivery chute, thecoarser or larger sizes of material being delivered from the uppermostscreen, and the finer or, smaller sizes are delivered from. the lowerscreens, the very finest being delivered from, the lowermost screen. Ihaveshown a simple and efiicient chute members 104, 105,106, areshown,re-,

spectively' associated with the uppermost, the

intermediate and v the lowermost screen.

screens, are preferably and as shown, connected to other by side plates01' mfimbers 107, whic are pivotally connected at their.

supper ends to a hinge rod 10.8, Iwhereby all;

of the delivery chutes may be rocked or swung together into raisedposition, when necessary or desired, to afford access to the lowerordelivery ends of the screen sections,

or for other purposes.

Itwill be seen that the hinge rbd108 is carried by framework withinwhiehthe screen .box is suspended, and hence the delivery chutes do notvibrate with the screen box and'scr'eens.v

If desired, and in order to prevent theflyingot dust, when the machineis operation, means'may be provided for confining the dust w thin themachine. I have showna simple arrangement for this pur ose, wherein a, I

cover. plate 109, shown'in t is instance as a corrugated sheet, isplaced over 'thefupper screen and is mounted and held in place withinthe screen box, between*'theisidemem-' bers of said box- I-alsoproyid'edust-cloths 110, around the bottom of the scr'eenbox.

screen box structure;

In this way the dual is ithi seen that I ptovidean exceedingly simpleFrom'th it be screen structure which is economical'to build and isefficient in operation, andwherein provision is made for altering therate of vibration or amplitude of vibration to suit various conditionsor characters of material to be. screened, wherein eflicient lubricationof the unbalanced pulley structure is secured, wherein the screen clothsare mounted and tensioned in a most simpleand effective man ner, andwherein the structure, as a whole, is self-contained and capable ofbeing transported and handled very conveniently and safely.

And while I have shown and described aspecific structure as anillustrative embodi: ment of my invention, I wish it to be understoodthat in its broadest scope, as defined in the claims, my invention isnot to be limited or restricted to the exact details of structure shownand described, as variations therefrom and changes therein mayreadily'occur to persons skilled in the art without depart-' ing fromthe spirit and scope of my invention.

But what I claim as new and useful andof my own invention, and desire tosecure by Letters Patent, is

1. In a vibrating screen structure, a framework including side memberseach having an upper and a lower beam disposed in parallel relation toeach other and connected and braced together, said side members being ofsaid intermediate members, and a screen cloth supported at its edgesupon said stringers and having cushion strips secured thereto, saidcushion strips resting on said oval surfaces.

4. i In a vibratory screen structure, a screen unit including a framehaving side stringers and intermediate members parallel therewith, ovalshaped strips carried at the'upper edges of said intermediate members,and a screen cloth supportedat its edges on said stringers and havingcontact strips secured theretoto rest on said oval strips.

5. I a vibratory screen structure, a screen unit including a framehaving side stringers and intermediate members parallel therewith, said"side stringers having a wear late applied as a facing to the uppersurface tliere= of, and a screen cloth supported at its edges upon saidwear plate and having itsgloody portion resting on said intermediatemembers, the inner edge of said wear plate being bent or curveddownwardly from the plane of the screen cloth. f

6. In a vibratory screen. box structurefa vibratory screen box includinglongitudinally extending side members, and transversely extending endmembers, said transversely extending end members being cut away on theirouter lower portions, in combination with a screen cloth resting at its.endupon a 'transverse end member, a plate fulcrumed at its upper edgeagainst the outer cut away surface of an end member and engaging the endedge of the cloth, and means to tilt said a plate to tension said cloth.In testimony whereof I have hereunto set my hand on this 9th day ofFeb., A. D. 1924.

GUSTAVE A. OVERSTROM.

